HPLC Determination of 8 Monoamine Neurotransmitters in Brain Tissues of Mice Contaminated with Paraquat and Their Changes After Contamination

HPLC was applied to the determination of 8 monoamine neurotransmitters (norepinephrine, epinephrine, levodopa, dopamine, dihydroxyphenylacetic acid, serotonin, 5-hydroxyindoleacetic acid and high vanillin acid) in brain tissues of mice contaminated with paraquat and their changes in mass concentrations during time intervals within 72 h after contamination. 36 mice were separated into 6 groups with 6 mice in each group. One of the group was taken as the reference group, while the remainder 5 groups were the contaminated groups staying for 6, 12, 24, 48, 72 h separately after contamination with paraquat by pouring down the throat a definite volume of paraquat solution giving 30 mg·kg^-1 of paraquat for each mouse. The mice of reference group were poured down with normal saline. At the end of each staying time, the mice were anesthetized with 1% sodium salt of pentabarbital and their brain tissues were taken and homogenized for 30 s with the tissue-homogenizing solution with its volume by the ratio of 1 g of brain tissue to 7.5 mL of the homogenizing solution. The mixture was centrifuged twice taking 15 min for each. The supernants were taken and used for HPLC analysis. Hypeisil GOLD aQ column (4.6 mm×250 mm, 5 μm) was used as the stationary phase, and mixtures in various ratios of methanol and 30 mmol·L^-1 KH₂PO₄-H₃PO₄ buffer solution (pH 4.6) were used as mobile phases in the gradient elution. Detections of peak areas of the 8 analytes were taken by fluorescence detector. Linearity ranges of the 8 analytes were obtained all within 1 000 μg·L^-1, with their detection limits (3S/N) in the range of 0.34-5.26 μg·L^-1. Replicate analysis of a sample was done and values of RSDs (n=5) were found ranged from 0.58% to 4.2%. Recovery was tested by standard addition method, giving recoveries in the range of 90.8%-106%. In further, changes of mass concentrations of each of the 8 neurotransmitters in the brain tissue after contamination with paraquat and within 3 days of staying were also determined and a reliable base for further study was provided.